City heights: the urban food waste dilemma

The diversity of an urban environment with its commercial establishments and varying population needs presents a big challenge when it comes to food waste. But anaerobic digestion may just be the answer, as Maxine Perella finds out

BiogenGreenfinch chairman John Ibbett watches on as chef Oliver Rowe demonstrates the art of sustainable cooking

Solving the urban food waste challenge by tapping into the potential of anaerobic digestion (AD) was the theme of an recent event held in London, hosted by BiogenGreenfinch and featuring celebrity chef Oliver Rowe who is renowned for his sustainable approach towards commercial cooking. Each year, about 7M tonnes of household food waste is thrown away - add to that commercial, catering and food processing waste and you're getting closer to 20M tonnes. There is now a big drive to divert that waste and according to Michael Chesshire, technology director of BiogenGreenfinch, AD represents the best opportunity to recycle and recover it.

"There has been so much interest in AD over the past two years, driven by its impact on the global environment because it is a low carbon process," he told delegates. "It will also reduce our dependency on mineral fertilisers through the production of bio-fertiliser and reduce road miles in the transport of food waste. It also produces renewable energy."

Chesshire cited strong government financial incentives for AD, which were going to strengthen further over the next two years. As from this April, AD qualifies for double ROCs (renewable obligation certificates) and by April 2010, renewable energy tariffs will be introduced which means those utilising electricity from AD will get a feed-in tariff - a guaranteed market value for that electricity over, say, 20 years.

In April 2011 renewable heat tariffs come into play, "so if you are getting beneficial use from the heat from AD not only do you have the value of that heat displacing fossil fuel, but there will also be a premium because it's green," explained Chesshire. Finally, in 2011-12 a biomethane tariff will be introduced for injecting biomethane into the national grid.

The Government has also set a target for 100 commercial and 1,000 on-farm AD plants to be built by 2020 under its Anaerobic Digestion - Shared Goals document published earlier this year. A task group has been set up to develop an implementation plan for the infrastructure needed to achieve this.

The costs to councils of using the AD route for food waste collection compared to in-vessel composting were examined in-depth by Dr Adrian Gibbs from consultancy Eunomia. He told delegates that using AD to process food waste collected separately could work out cheaper than processing co-mingled food and green waste together in an in-vessel composting plant.

Cost comparisons for councilsSpeaking about the findings of a recent study he worked on, Dr Gibbs said that sending food waste to AD and green waste to windrow composting cost councils on average £9.50 in gate fees per household per year, whereas sending co-mingled green and food waste to an in-vessel facility costs £10.80 per household. In addition, collecting food waste alone and sending it to an AD plant costs £5.50 per household over the same period.

"While average gate fees for AD facilities are higher than in-vessel composting, overall AD is cheaper," he concluded. He added that councils shouldn't over-complicate their food waste collections and strongly advised against mixed waste solutions. "I implore you - don't go for wheeled bin collections for garden and food waste, don't mix it up. If you add food waste to garden waste you get seasonal impacts - for example, lots of garden waste in summer but not in winter."

This not only impacts upon the collection operation, said Dr Gibbs, but if you collect both together all material has to be treated in an enclosed process due to Animal By-Products regulations - this can prove an expensive option as garden waste can be treated much more cheaply through open windrow composting. He added that over the past two years, more and more councils were choosing to operate separate food waste collections.

"If you were to ask me in 2007 what local authorities were doing, I'd have to say that 44 of them were co-collecting food and garden waste and only 11 were operating dedicated food waste collection services. But by April 2008, 56 were co-collecting compared to 54 which are now operating dedicated food waste collection services."

London gets its priorities rightTackling food waste is one of six priority materials identified by the London Waste & Recycling Board (LWRB). Antony Buchan, the board's policy & project manager, told delegates that energy production from food waste was "one of the most viable and appropriate solutions".

In its first round of funding calls, the LWRB received 142 expressions of interest, 30 of which are proposals for either the development of AD facilities or for projects directly linked to AD. He stressed that for proposals to be successful, they had to fulfill certain criteria, once of which was design excellence. The board is looking at how "waste facilities can integrate into urban environments as this is critical for overcoming probably the biggest hurdle - planning," and also optimal location, where facilities can be co-located alongside potential feedstock providers or end-market users such as supermarkets to provide closed loop logistical solutions.